Method of manufacturing an electrotype in a mold provided with a gasket



Sept. 11, 1956 H l. BISHOP 2,762,098

METHOD OF MANF'ATURING AN ELECTROTYPE IN A MOLD PROVIDED WITH A GASKET Filed Dec. 23, 1953 3@ 50 42 JUE-4v INVENTOR.

-MEE L. B/SHP /0 /6 52 BY I 315.5 IIE. 7 WZ? @LMV United States Patent Office 2,762,098 Patented Sept. 11, 1956 METHOD OF ACTURING AN ELECTRO- TYPE 1N A MOLD PROVIDED WITH A GASKET Homer L. Bishop, Dayton, Ohio, assigner of thirty percent to Earl E. Stansell, West Carrollton, Ohio Application December 23, 1953, Serial No. 400,076

3 Claims. (Cl. 22-204) rIhis invention relates to an asbestos blanket or gasket member underlying a shell, the method of making an electrotype plate for use in connection with the manufacture of electrotype plates.

In the manufacture of electrotype plates, diculty is encountered in holding the shell in the bottom of the mold while casting molten casting metal on the rear side of the shell. In the iirst place, there is a tendency for the shell not to lie perfectly flat in the bottom of the mold cavity. There may be slight bulges in the shell, permitting metal to flow on the under side or the face of the shell, to thereby produce defective electrotype plates. Furthermore, if metal does ow on the under side of the shell, there is a tendency for the shell to float, in that the specific gravity of copper is much lower than the specic gravity of lead, which is the principal metal used in the backing material.

An object of this invention is to provide a blanket or a cushion on the under side .of the shell positioned between the shell and the bottom of the mold which functions in some respects in a manner similar to a gasket and forms a seal between the shell and the bottom of the mold.

Another object of this invention is to provide a pluralityof resilient members closely spaced together throughout the entire rear area of the shell used in holding the shell rmly against the blanket functioning as a gasket, to thereby prevent metal from flowing on the under side of the shell and furthermore to prevent the shell from iloating to the top lor towards the top of the molten metal during the casting operation.

Other objects and advantages reside in the construction of parts, the combination thereof and the mode of operation, as will become more apparent from the following description.

In the drawings, Figure 1 is a top plan view, with parts broken away, of a mold having a shell mounted therein and means mounted above the shell for holding the shell in position.

Figure 2 is a cross sectional view of the mold, the cushioning or gasket member, the shell and the resilient means for holding the shell in position.

Figure 3 is another cross sectional view similar to Figure 2, showing the molten metal applied to the rear of the shell.

Figure 4 is a cross sectional view showing the mold, the shell and the cushioning member or gasket member after withdrawing the resilient retaining member shown in Figure 3 from the molten metal and after the molten metal has solidiied.

Figure 5 is an enlarged, perspective view of a resilient member used to hold the shell in the bottom of the mold cavity.

Figure 6 is a fragmentary end view of a mold and the capping member.

Figure 7 is a cross sectional view of the mold with the cast metal in place underneath a shim.

Referring to the drawings, the reference character 10 indicates a mold having a mold cavity 12. The bottom of this mold is flat throughout its entire area. The margins of the mold may be provided with an outwardly directed tlange 14 extending throughout the entire periphery of the mold cavity. In preparing the mold for the casting operation, an asbestos blanket or cushioning member 16 is placed in the bottom of the mold cavity. Although the cushioning member or gasket 16 is referred to as being made from asbestos, it may be made from any suitable material having the desired characteristics. After the cushioning member 16 has been placed in the bottom of the mold, a shell 18 is superimposed upon this gasket 16. The shell 18, as is well known to those skilled in the art, is generally made from copper, the face of which may be plated with nickel or chrome and the rear covered with a coating yof tin.

Due to the fact that the asbestos blanket 16 and the shell 18 have a specific gravity that is far less than the specific gravity of lead, the principal ingredient of the casting material, there is very definitely a tendency for the gasket 16 and the shell 18 to rise towards the top, especially if the casting material has an opportunity to flow on the under side of any portion of the shell or the gasket.

In order to prevent metal from owing on the under side, it is desirable to hold the shell and the gasket member lirmly against the bottom of the mold cavity and to hold the shell in a perfectly at position, so that there is practically no opportunity for the casting metal to ow under any portion of the shell or any portion of the gasket. It is not suiiicient to merely place the gasket and the shell in the bottom of the mold cavity and rely upon the weight of these members to hold these rmly against the bottom of the mold cavity, in that the shell or the gasket may be warped slightly, may be wrinkled .or may be curved slightly, so as to have a tendency to pull portions away from the bottom of the mold cavity, leaving a gap into which the molten metal will ow. As soon as the molten metal ows on the under side of the shell or the gasket, there is atendency for the shell and the gasket to rise, thereby ruining the electrotype. v

In order to overcome this diiculty, a capping member 30 has been provided, which has a width equal to the width of the mold and has flanges 32 extending along two sides thereof. This capping member 30 is superimposed upon the mold, the ilanges 32 registering with the flange 14 of the mold proper. The capping member 30 is in reality an inverted channel-shaped member, in that the ends are open.

The capping member 30 is provided with a plurality of apertures receiving the stems 34 .of the spring members 36. Each of the spring members 36 is provided with a downwardly projecting shank 38 that may be formed into a suitable contour, as for example, a substantially circular portion 40. The upper end of each stem 34 is bent at right angles, as shown at 42, preventing the spring members 36 from being removed from the capping member 30. When member 30 is positioned upon the mold, the springs 36 are in compression, so as to cause the circular portions 40 to exert a pressure against the top of the shell. Spring members 36 are mounted in close proximity to each other, so as to cover practically the entire rear surface of the shell. 'Ihe capping member 30 terminates at 50, leaving an opening between the mold and the edge of the capping member 30, into which the molten metal may be poured or may ow. The mold may be similar to the molds used in my copending application for Letters Patent Serial No. 285,818, led May 2, 1952 for Method of and Apparatus for Casting Electrotypes.

In order to eliminate any possibility of blow holes caused by foreign matter gasifying when the molten metal is poured, the temperature of the mold, the capping member, the springs, the shell and the gasket member is raised, so as to be the same as the temperature of the molten metal. For purposes of convenience, this temperature is referred to as a fnormalized temperature. When the mold and the parts 'carried thereby have the same temperature as the molten metal, the mold may be dipped into molten metal without any particular stresses being set up in the parts associated with the mold, caused by some other temperature than a normalized temperature. Furthermore, by holding the mold in the molten metal for a suicient period of time, if perchance there should happen to be any dust particles or foreign matter tending to gasify, such foreign matter is permitted to gasify and the gas to escape towards the top of the molten metal before removing the mold from the vat of molten metal.

Due to the fact that the rear side or the upper side of the shell when it is placed in the mold, as seen in Figure 2, is tinned, and due to the fact that tin oxidizes very readily when heated, the normalizing temperature is applied to the shell for only a short period of time before the shell and the mold are submerged in the molten metal, to thereby prevent oxidation. In the event the rear of the shell oxidizes, an unsatisfactory bond is produced.

After the mold is removed from the molten metal, member 30 andthe springs carried thereby are carefully raised and removed from the mold. Due to the fact that the shell has been held in contact with the gasket member and the gasket member has been held against the bottom of the mold cavity, no molten metal has owed under these parts and that being the case, the weight of the molten metal on the rear of the shell holds these parts in position in the bottom of the mold. The capping member 30 and the springs mounted thereon, together with the retaining portions 40 are removed before the metal solidies and before the metal begins to crystalize.

After the metal has begun to solidify, a shim 52 may be placed on top of the metal, the capping member 30 again inserted on top of the metal, with retaining portions 40 exerting a pressure against the shim overlying the metalV that has solidified, thereby tending to compress and consolidate the cast metal, so that in the event there are any voids or blow holes7 these will be eliminated by this pressure.

Suitable clamping means, not shown, may be used in holding the capping member 30 in position, both whenV` pouring the molten metal into the moldV and when the pressure is exerted to the rear of the shim placed on top yof the metal that is in the process of soliditication.

Although the preferred embodiment of the device has been described, it will be understood that within the purview of this invention various changes may be made in the form, details, proportion and arrangement of parts, the combination thereof and mode of operation, which generally stated consist in a device capable of carrying out the objects set forth, as disclosed and denedin the appended claims.

Having thus described my invention, I claim:

l. The method of manufacturing an electrotype utilizing a mold having a cavity provided with a flat bottom, said method including the stepsof inserting a gasket member in the bottom of the mold, inserting a shell upon the gasket member, applying pressure over the entire shell area independently of the mold so as to hold the shell and the gasket member firmly against the'bottom of the mold, pouring molten metal into the mold on. top Y of the shell held against the gasket member, removing the pressurev applied to the shell before the molten metal solidies, and cooling the molten metal to cause it to solidify.

2. The method according to claim 1, including the steps of placing a shim on top `of the metal after itsolidifies, and applying a yieldable pressure on top of the Vshim to consolidate the metal.

3. The method of manufacturing an electrotype according to claim l, wherein the following steps are included: heating the mold to substantially the temperature Y of the molten metal before inserting the gasket member and the shell and briey heating the gasket member and the shell to raise the temperature of the shell to the temperature of the molten-metal before, pouring the molten metal on top of the shell.

References Cited in the le of thisy patent UNITED STATES PATENTS 17,741 Jocelyn Iuly 7, 1857 35,986 Beach Iuly 29, 1862 250,238 Hansen Nov. 29, 1881 1,009,390 Droitcour Nov. 21, 1911 1,073,105 Dunton Sept. 16, 1913 1,905,048 Norris et al. Apr; 25, 1933 1,927,262 Gould et al. Sept. 19, 1933 2,507,347 Myers May 9, 1950 

